CHICAGO — Mayor Richard Daley has announced a plan to dramatically slash emissions of heat-trapping gases, part of an effort to fight global warming and become one of the greenest cities in the nation.

The plan calls for reducing greenhouse gas emissions to three-fourths of 1990 levels by 2020 through more energy-efficient buildings, using clean and renewable energy sources, improving transportation and reducing industrial pollution.

"We can't solve the world's climate change problem in Chicago, but we can do our part," said Daley on Thursday. "We have a shared responsibility to protect our planet."

It's the first step toward cutting emissions to one-fifth of 1990 levels by 2050, as called for in the 1997 Kyoto global warming protocols.

Next month, the City Council is expected to consider an ordinance that would update the city's energy code to require such things as better insulation, heating and cooling systems and windows in all commercial, industrial and residential buildings.

The city also has an agreement with two coal-fired power plants to reduce emissions or shut down by 2015 and 2017, respectively.

The plan also calls for expanding the number of green rooftops, increasing recycling and car-pooling and promoting alternative fuels.